We are developing Drosophila melanogaster as a model system to understand the molecular basis of rapid ethanol tolerance. Sedating Drosophila for 15 minutes with ethanol causes detectable ethanol tolerance 24 hours later. Concomitant with tolerance, we observe an increase in expression from a Ca2+-activated K+ channel gene. This channel gene is called slo. Mutations in slo prevent the appearance of tolerance, while artificially increasing expression produces resistance. In addition, we observed that reduced expression of slo is associated with ethanol sensitization. Our data indicate that there is a causal relationship between the level of slo expression and tolerance and sensitization. It also strongly suggests that increased slo expression enhances neural activity and that decreased slo expression depresses neural activity. To test this hypothesis, inducible transgenes that express slo channels will be used to produce adult animals that differ in their expression level of the gene. An electrophysiological assay will be used to determine if increased expression is associated with increased neural activity. A measure of behavioral activity will also be used to determine if increased slo expression results in increased behavioral activity. We have observed that during ethanol sedation the overall spike frequency in the brain is reduced. We will determine if the increase in slo expression is a direct response to this reduction in reduced neural activity. Furthermore, we will determine if a transitory reduction in neural activity, by itself, gives rise to measurable alcohol resistance. To do so, we will use a Drosophila mutation that causes reduced neural activity in a temperature-dependent and reversible manner. With this mutation, a temperature pulse will be used to reduce neural activity. The following day, we will determine if the expression level of the slo gene has increased and we will determine if the animals have acquired alcohol resistance.